1. Field of the Invention
The present invention relates to an image forming apparatus, which uses a plurality of beams, such as a copier, a facsimile machine, and a printer, and in particular, to a method of improving the image quality of an image formed by the image forming apparatus.
2. Description of the Background Art
Conventionally, many image forming apparatuses of this type which scan with a plurality of beams concurrently and select a leading beam from among the plurality of beams such that color shifts may be prevented are disclosed in, for example, Japanese Patent Laid-Open No. 10-104537 and Japanese Patent Laid-Open No. 2002-072607. In this prior art, when image formation is performed by using a plurality of beams, writing is started from a headline of the image in each color with a different beam so as to decrease shifts between superimposed images. Nevertheless, when the writing of the beginning line of an image, i.e., a top line is started with different beams, there is a possibility that image unevenness arises in a superimposed image.